1. Field of the Invention
The present invention relates to a keyboard switch suitable for use in a notebook-type personal computer having a lid that closes to cover at least one key top. More particularly, the present invention relates to an improved keyboard switch that allows a cover-closing motion to move the key tops downward and allow the cover to easily close without undue ware.
2. Detailed Description of the Related Art
It is conventionally known to move key tops downward during a closing motion and accommodate a keyboard switch in a closed notebook-type personal computer.
Referring now to FIGS. 12 to 14, showing a conventional keyboard switch 100 as disclosed in the publication of Japanese Patent No. 2857353, includes a supporting plate 107 for supporting a large number of key tops 102. Each key top 102 is attached to a cross link 101. Keyboard switch 100 is included between a lid 115 and an equipment case 109 of a conventional notebook-type personal computer.
Cross link 101 includes a first link member 101a and a second link member 101b, each formed generally in the shape of the letter xe2x80x9cUxe2x80x9d, and being rotatably linked together about an intermediate rotatable fulcrum (not shown). Cross link 101 guides key top 102 during motion in an up-and-down movement.
In the operational position shown in FIG. 13, a dome-like rubber elastic portion 114 is disposed below each key top 102 and serves as a return spring, pressing key top 102 upward in response to a key stroke. Elastic portion 114 abuts the bottom surface of a pressure-applying portion 106 formed at the intersection between first and second link members 101a, 101b. 
Elastic portion 114 is integrally formed on a rubber sheet 104 superimposed on a switch sheet 103. Switch sheet 103, is located below elastic portion 114, and includes an integrally formed switch portion 103a. Rubber sheet 104 and switch sheet 103 are both flexible and are superimposed and generally laminated together forming a flexible sheet that is slidable along a guide rail 108 included in supporting plate 107. Switch sheet 103 and rubber sheet 104 are contactable with a return spring 118 and disposed between their end portions (not shown) and equipment case 109. The laminated flexible sheet 103 and rubber sheet 104 are loaded by return spring 118 with a force that tends to move them toward the left-hand portion in FIGS. 12 through 14.
In the operational position shown in FIGS. 12 and 13, when downward pressure is applied to key top 102 from above, key top 102 is guided by cross link 101 and is thereby moved downward and kept generally horizontal relative to equipment case 109 without being significantly inclined. As a result, pressure-applying portion 106 of key top 102 presses on and deforms elastic portion 114, so that an xe2x80x98ONxe2x80x99 operation of switch portion 103a is effected.
Equipment case 109 is rotatively coupled to lid 115 and rotates closed to protect key tops 102. A cam projection 117 projects outward from the inside of lid 115. Cam projection 117 has a top surface formed as an inclined plane. During a lid 115 closing-motion, the top surface of cam projection 117 presses on a side surface (not shown) of both switch sheet 103 and rubber sheet 104. As the top surface of cam projection 117 presses on the side surfaces of both switch sheet 103 and rubber sheet 104 the inclined plane exerts a force that acts to counter the spring force supplied by return spring 118. As a result of this counter-action, both switch sheet 103 and rubber sheet 104 move toward the right-hand side of FIGS. 12 and 13. As a result, when lid 115 is rotatably closed toward equipment case 109, switch sheet 103 and rubber sheet 104 are slid, in a synchronization with lid 115, into a retracted position and key tops 102 are lowered toward support plate 107.
During closing, dome-like rubber elastic portion 114 and switch portion 103a retract into the lower portion of a housing concave portion 116 formed in key top 102. Also during closing, an upward projection 104a, projecting from rubber sheet 104 and located near the lower leg portion of first link member 101a, contacts first link member 101a and forces cross link 101 into a retracted position as rubber sheet 104 slides leftward, as shown in FIG. 14. Thus, simultaneous with the motion of elastic portion 114 and cross link 101, key tops 102 move into the retracted position, reduce the overall height of keyboard switch 100, and allow keyboard switch 100 to fit within equipment case 109.
It should be recognized that, while key top 102 move downward into the retracted position, switch portion 103a remains deactivated. It should also be noted, that when key top 102 is in a retracted position, elastic portion 114 maintains an un-compressed state within concave portion 116, thus reducing the material fatigue and increasing the operational life of elastic portion 114.
During opening, lid 115 is rotated away key tops 102 and cam projection 117 loses contact with switch sheet 103 and rubber sheet 104. As cam projection 117 loses contact with switch sheet 103 and rubber sheet 104, return spring 118 forces both switch sheet 103 and rubber sheet 104 leftward into the operation position shown in FIG. 13. In the operational position, key top 102 is supported by elastic portion 114 through cross link 101.
It should be additionally noted that the above-described action of conventional keyboard switch 100, shows one possible way to reduce the thickness of the equipment case 109 and hence the overall thickness of a notebook-type personal computer. It should also be noted that in conventional keyboard switch 100, switch portion 103a is not activated during the closing motion and elastic portion 114 is kept in an extended state.
Additionally, in the conventional keyboard switch 100, the inclined plane of cam projection 117 both horizontally and vertically presses on the contact surface of switch sheet 103 and rubber sheet 104. While the horizontal-pressing motion of cam projection 117 is generally desirable in this device to activate key tops 102, the vertical- pressing motion subjects switch sheet 103 and rubber sheet 104 to undue stress and fosters the formation of an undesirable warp along the contact surface of both sheets. Consequently, it is very difficult to achieve either a smooth sliding motion as lid 115 rotates relative to equipment case 109 or sufficient durability in switch sheet 103 and rubber sheet 104.
Moreover, while the horizontal-pressing motion of cam projection 117 is generally desirable to activate key tops 102, the horizontal-pressing motion also subjects switch sheet 103 and rubber sheet 104 to a compressive stress in the sliding direction. This compressive stress fosters the formation of an undesirable warp throughout flexible switch sheet 103 and rubber sheet 104. A reinforcing lining sheet 121, made of metal, is applied to the back surface of switch sheet 103 and rubber sheet 104 to counteract the formation of this undesirable warp. Unfortunately, lining sheet 121 increases the overall thickness of keyboard switch 100 which results in an increase in the overall thickness of a notebook-type personal compute and an increase in cost.
Furthermore, return spring 118 requires a relatively heavy spring-force to operate switch sheet 103 and rubber sheet 104 between the operational position and the retracted position and creates an increasingly complex construction.
It is an object of the present invention to provide an improved keyboard switch that offers durability while requiring only moderate physical force during an opening and closing operation.
It is another object of the present invention to provide an improved keyboard switch that does not require a return spring and thus retains a simplified configuration.
It is another object of the present invention to provide an improved keyboard switch that allows a thin flexible sheet to reciprocate in synchronization with an opening and closing motion of a lid.
The present invention relates to a keyboard switch including an improved interlock mechanism that actuates a switch sheet from a first position to a second position and correspondingly narrows a gap between a key top and the switch sheet. The interlock mechanism converts a rotary motion from a device lid to a linear motion for the switch sheet guided by a slider block slidably retained in a device case.
According to an embodiment of the present invention there is provided an a keyboard switch, comprising: a support plate supporting a plurality of keys inside a device case; an interlock moving the keys from a first to a second position; the interlock including a cylindrical cam that rotates about a pivot shaft; the pivot shaft rotatably fixed in a bearing plate for pivotally connecting the cylindrical cam to an equipment case, the cylindrical cam including a radial interlocking plate for pivotally connecting the cylindrical cam to an equipment lid, the cylindrical cam including a cylindrical body, the cylindrical body including a cam grove, a slider having a follower fitting slidably inside the cylindrical cam and movably captured in the cam grove, the slider having a slider body extending away from the cylindrical cam, the slider including a slider block, the slider block extending perpendicularly from the slider body, the slider block slidably engaging a guide grove formed in the equipment case, an rigid angle plate fixedly attached to the slider, a switch sheet fixedly attached to the angle plate allowing the switch sheet to slidably reciprocate with the angle plate, and the interlock causing the switch sheet to slidably reciprocate in response to rotational operation of the lid whereby the interlock converts the rotational motion to a linear motion.
According to another embodiment of the present invention there is provided a keyboard switch, further comprising: a short portion, a long portion, and a coupling piece included in the rigid angle, the long portion extending perpendicular to the short portion, the switch sheet fixedly attached between both the short and the long portions, the coupling piece extending perpendicular from the long portion, and the coupling piece fixedly attached to the slider whereby transmitting the linear motion to the switch sheet is accomplished without crimping the switch sheet.
According to another embodiment of the present invention there is provided a keyboard switch, further comprising: at least one hole in the long portion, at least one rivet affixing the long portion to a first side of the switch sheet through the hole, a U-shaped portion on the short portion, and the U-shaped portion fixably engaging an orthogonal side of the switch sheet whereby the switch sheet is affixed between the first and second sides.
According to another embodiment of the present invention there is provided a keyboard, comprising: at least one keyboard switch in the keyboard, a keyboard cover, means for actuating the at least one keyboard switch to a retracted position in response to closing the keyboard cover, the means for actuating including a coupling piece, the means for actuating further including a cam actuated by the closing to displace the coupling piece, a first guide element affixed to the coupling piece, a second guide element affixed to the keyboard, and the first and second guide elements being effective for guiding displacement of the coupling piece, whereby precise retraction of the at least one keyboard switch is attained when the keyboard cover is closed.
According to another embodiment of the present invention there is provided a keyboard, further comprising: a plurality of keyboard switches in the keyboard, and the means for actuating retracting the plurality of keyboard switches to the retracted position in response to closing the keyboard cover.
According to another embodiment of the present invention there is provided a keyboard, wherein: the first guide element is a slider block, the slider block extending away from the coupling piece, the slider block being substantially shaped as a parallelepiped having a first and a second side, and the slider block and the second guide element are effective -for guiding displacement of the coupling piece, whereby precise retraction of the plurality of keyboard switches is attained when the keyboard cover is closed.
According to another embodiment of the present invention there is provided a keyboard, wherein: the second guide element is guide groove, the guide groove shaped to slidably receive the slider block, the guide grove contacting the first and second side of the slider block, and the slider block sliding in the guide grove in response to closing the keyboard cover whereby precise retraction of the plurality of keyboard switches is attained when the keyboard cover is close.
In this construction, the switch sheet is guided along the sliding direction by the supporting projection loosely received in a slit in the switch sheet. This eliminates the need for an extra guiding member.
The above, and other objects, features and advantages of the present invention will become apparent from the following description read in conjunction with the accompanying drawings, in which like reference numerals designate the same elements.